INTERNATIONAL PATENT APPLICATION NO. PCT/FR99/01698, PUBLICATION NO. WO00/01961
The present invention relates to a hydrokinetic coupling apparatus with a lock-up clutch, of the type which is described in French patent application No. 98/04216 of Mar. 31, 1998.
More precisely, such a hydrokinetic coupling apparatus comprises a turbine wheel which can be coupled to a driven shaft and which is contained within an impulse wheel casing with which it is able to cooperate, for hydrokinetically transmitting a torque to the said driven shaft, from a driving shaft which is able to be coupled with the said impulse wheel, the turbine wheel and/or the impulse wheel being made in the form of a wheel which comprises an outer toroidal portion fixed on a hub, together with blades fixed to the said outer toroidal portion, and possibly an inner toroidal portion.
The operation of such a hydrokinetic coupling apparatus is well known, and will only be repeated below by way of reminder.
Hydrokinetic coupling apparatus of the above type can be applied in particular to motor vehicles, and, as is known in such applications, reduction of the number of components, and saving of weight, are constant concerns with a view to obtaining a cost advantage. More precisely, the invention concerns the construction of a wheel which includes an outer and/or an inner toroidal portion, together with blades which are fixed thereto, the said bladed wheel being able to be used, in a hydrokinetic coupling apparatus of the kind in question, as either an impulse wheel or a turbine wheel, being for example moulded in a synthetic material. In that document FR98/04216, the bladed wheel is made in three parts. It is desirable to simplify this wheel.
Therefore, the invention relates, apart from the construction of this bladed wheel and its different parts, to the construction of the said inner toroidal portion, the assembly of the outer and inner toroidal portions together by means of the blades, the means for coupling the outer toroidal portion to the hub, and finally the assembly of the said bladed wheel to the cover plate in the case where it is an impulse wheel, the various objects of the invention being in all cases to obtain:
a reduction in weight with synthetic materials that replace steel,
a reduction in cost, with simplification of the manufacture of a turbine or impulse wheel in one or two pieces, in particular by reduction in the number of operations during the manufacturing process, as compared with the case where these components are made of steel,
an improvement in regard to fluid losses as compared with a conventional steel product (leaks between the blades and the toruses), and
a gain in output for the apparatus, with moulding of the turbine or impulse wheel blades enabling a more complex form to be obtained in the blades, leading to improved flow of the fluid.
In accordance with a main arrangement of the invention, a hydrokinetic coupling apparatus of the type defined at the beginning of this document is characterised in that the blades and the toroidal portion are moulded in one piece in a synthetic material, which consists of a thermoplastic material, a thermosetting material, or an alloy of synthetic materials, the said materials being capable of being reinforced with strengthening fibres.
Preferably, the said strengthening fibres are glass fibres, xe2x80x9cKevlarxe2x80x9d fibres, etc.
Preferably, the moulded turbine wheel has a thickened peripheral portion which enables it to contain arched seatings for the springs which couple it with the clutch disc.
Thanks to the invention, a sub-assembly consisting of the blades and the toroidal portion is obtained in a simple and inexpensive way, which enables the number of components to be reduced and enables a sub-assembly to be easily made in synthetic material, given that it is very difficult to make such a wheel, especially a turbine wheel, integrally.
In this connection, the mould is then very complex. Furthermore, the blades can take a more complex form and accordingly give better performance from the dynamic point of view.
Thanks to the invention, in one embodiment the wheel does not have an inner toroidal portion.
In other embodiments a stabilising hub, separate from the toroidal portion, is provided on the free side of the blades for stabilising the latter. This arrangement enables any distortion of the blades to be avoided in operation.
The means consists of a crown or a toothed disc, which may or may not be of profiled form, for maintaining the spacing between the blades and stabilising these latter.
In another version, the means consists of the other toroidal portion.
The said other portion may be of metal or of synthetic material.
In one embodiment, the blades are inclined so as to permit stripping from the mould with helical relative movement between the mould and the component.
This operation can easily be carried out.
Where the blades are straight, stripping from the mould may easily be carried out axially.
The toroidal portion made by moulding integrally with the blades may be the inner toroidal portion or the outer toroidal portion.
In another version, the blades are formed partly from the inner toroidal portion and partly from the outer toroidal portion, and are then assembled together in the region of their free ends, for example by adhesive bonding, or indirect application of heat, for example by laser welding.